A friend of mine recently decided it was time to let go of her old Palm Tungsten E2 in favor of her iPod touch. The biggest problem was converting her old contact database from the Palm desktop app. We managed to export everything when she was on her old iMac running Tiger, but we ran into fatal problems with her new iMac and Snow Leopard, so we had a lot of editing to do before it was ready for the touch.
Due to outdated and duplicate entries, we pared her address book down from 1019 entries to 765. The problem? We couldn't get her MobileMe account to see the new, slimmer file, nor could we do a direct sync with iTunes. For some odd reason, it seemed like there were two files, one (765) seen by Address Book and one (1019) seen by everything else.
After trying to sync, forcing the computer to overwrite MobileMe, deleting the computer from the sync, adding it back to sync and other contortions (including naughty words!), I logged into Apple's online chat/tech site. The tech had me do mainly the same things I had already tried, and after an hour of unproductive work, I thanked her for her time, and did what I should have to start with.
When in doubt, go to a clean account. I exported a copy of the Address Book to an archive file, then moved it to the Shared folder in the Users folder. I logged out of her main account and into a test account that I created when I was troubleshooting something else on this computer. Then it was time to import the archive into the clean Address Book. Nope, no, not gonna do it. I can only guess that there was something in the original file that was causing all of the problems.
I went back into the main account, selected all of the entries and exported to a single vcard. Once back in the Test identity, I dragged the vcard into Address Book, and almost immediately I had all of the entries — minus her groups. Can't win them all. I synced the new Address Book with MobileMe, logged back into the main account and immediately was hit with "Your Address Book contents have changed. Do you wish to merge, overwrite or ignore?" Overwrite, here we come. Wherever the glitch was, it appears to be gone. I have it set to push changes over MobileMe, and so far it seems to be working.